Mixed base code generation



May 5, 1964 R. E. WILLIAMS MIXED BASE CODE GENERATION 7 Sheets-Sheet 1 Filed July 24, 1958 RESET O T .So m m .T D mgm wzjm E s T .d V

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BY z! ATTORNEYS May 5, 1964 R. E. WILLIAMS MIXED BASE coDE GENERATION '7 Sheets-Sheet 7 Filed July 24, 195s mmm mmm

1 N VENTOR RICHARD E. WILLIAMS ATTORNEYS United States Patent Oilce 3,132,334 Patented May 5, 1964 3,132,334 MKXED BASE .CODE GENERATIN Richard E. Williams, Fairfax, Var., assigner, by mesne assignments, to Melpar, luc., Falls Church, Va., a corporation ot Delaware Filed July 24, 195i?, Ser. No. 750,828 22 Claims. (Cl. MOM-347) The present invention relates generally to pulse coding and decoding by means of mixed base techniques, and more particularly to mixed base modulation and demodulation techniques wherein are employed a variety of modulation methods, including pulse amplitude modulation, pulse width modulation, pulse position modulation subcarrier modulation and combinations of these modulations, applied to a single pulse. i

ln accordance with the present invention, mixed base digital Words are employed, wherein each digital word corresponds with a series of digits rooted each in a different base, as distinguished from the conventional digital Word wherein all thedigits are rooted in the rsame base system. lt may be shown, in such case, that if the roots, bases or moduli ofthe system are relatively prime, i.e. have no common factor other than one, that a sequence of digital words may be generated which contain no ambiguities over a range of Words equal to the product of the moduli, Such words may be generated by simultaneously adding units to each order or line of a word, Without carry from one order to another, which leads to techniques for rapid processing in the arithmetic functions, and which requires particularly uncomplicated circuitry. Physical quantities of analogue nature may have their magnitudes converted to mixed base notation, for transmission to remote locations in telemetric systems, the use of mixed base notation presenting for this application advantages over binary, binary-decimal or decimal notation, in many respects. While avoidance of carry in arithmetic computation is one advantage, in computing with mixed base numbers, the use of bases or moduli which are adjacent in value permits the transmission of quantized signals employing similar increments of value in the several orders of a mixed base number. For example, by using moduli 9, l0, 11 each digit of a word varies from an adjacent value by about and this is true of all the digits of the number. 'Approximately 1,000 diierent magntiudes may be transmitted by means of three numbers, eachot which rnay assume approximately ten discrete values, all the values` being of the same order of magnitude. lt follows that high accuracy telemetric systems may be vastly simplified.

It isthus seen that each number iny a mixed base code maybe represented as a multi modulo or mixed base word, i.e. each number is represented by a plurality of separate numerals having a separate, relatively prime base or radix. Thus, the rigital number twenty may be represented as a mixed base word having three separate moduli or bases 9, l0, ll by the separate numerals 2, 0, 9.

ln accordance with'the present invention, mixed base words are recorded on tape, or are otherwise stored. The stored words may derive from any one of a number of sources, such as computers, transducers, or the like, and represent information. mitted to a remote location, preferably in the form of modulated pulses, and to be demodulated at the remote location or reconverted to mixed base Words.` Modes of modulation which may be employed include serial pulses, which may be AM, PWM or PPM modulated, or parallel pulseswhich may be frequency modulated. Additionally, pulses may be utilized each of which is modulated in plural modes, and an exemplary system is described and illustrated employing single pulses each of which is modulated in amplitude, width and frequency, according to This information is to be transthree digits of a mixed base tri-modulo word. Thereby, the possibility exists of transmitting an extremely large numberkof values by means of a single pulse. For example, a single pulsedcarrierhaving nine possible Values of amplitude, ten possible values of width and eleven possible values'of carrier frequency, may transmitan item of information, in a fraction of a microsecond, with a resolution of approximately one part in a thousand.

lt is, accordingly, a broad object of the present invention to provide systems for converting mixed base words to serial or parallel pulse code groups, wherein the pulses are either AM, PPM or PWM modulated, and to provide demodulators for such systems;

lt is another object of the present invention to provide a system for converting a rnixed base word to a single pulse having plural characteristics, each characteristic being representative of the value of one digit of the mixed base Word. t

lt is another object of thepresent invention to provide a system of code conversion, wherein an input code consists of a multi-modulo word, the digits of which exists simultaneously/in positional form, and wherein an output code consists of a multi-modulo word the digits of which are generated sequentially as modulations of pulses.

lt is still another object of the present invention to provide a system of code conversion, wherein an input code word consists of multiple digitseach based on a diterent modulus, and wherein the output code consists of a single pulse having various or" its characteristics representative of different digits of the mixed base word.

lt is a more specific object of the invention to provide a system for translating recorded mixed base words to pulsed signals, the pulses of which are modulated to represent the unixed base words.y

Itis a generic aspect of the invention to provide modulators and demodulators'capable of code conversion in mixed base' notation.

kThe above and still further objects, features and advantages ofthe present invention will become apparent upon consideration of the following detailed description of several specic embodiments thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FGURE l is a conventionalized representation of an indicia bearing tape, and read-out electrodes ior the indicia, wherein ytheindicia are coded in mixed base notation;

FIGURE 2 is a block diagram of a system for converting mixed base code, read-out of the tape of FlGURE l, to pulse amplitude modulated code;

FlGURE 3 is a representation oi a group of amplitude modulated pulses, as generated by the system of'FlGUlE FIGURE 4 is a block diagram of a demodulator for the pulse amplitude modulated signals generated by the system of FlGURE 2;

FIGURE 5 is a block diagram oi' a system for converting mixed coded signals to pulse width modulated signals;

FlGURE 6'is a representation of the pulse shapes of signals generated by the system of FIGURE 5; 7 FIGURE 7 is a block diagram of a demodulator for demodulating the signals generated by the system of FIG- URE 5;

FIGURE 8 is a blockdiagram of a system for converting mixed base code to pulse position modulated signals;

FlGURE 9 is a'representation of the character of the signals generated by the system of FlGUlE 8;'

FlGURE l0 is a block diagram of a demodulator for signals of the type generated by the system of FIGURE 8;

FIGURE ll is a block diagram of a system for con verting mixed base signals to sub-carrier frequency modulated signals;

FIGURE l2 is a representation of the frequencies of signals generated by the system of FIGURE 11;

FIGURE 13 is a block diagram of one modification of a demodulator capable of demodulating the signals generated by the system of FIGURE 11;

FIGURE 14 is a block diagram of a modiiication of the system of FIGURE 13;

FIGURE 15 is a block diagram of a system for converting mixed base coded signals to single pulses wherein each pulse has a plurality of characteristics, each representative of a different digit of a mixed base word; and

FIGURE 16 is a block diagram of a demodulator system for the signals generated by the modulator of FIG- URE 15.

Referring nowmore specifically to the accompanying drawings, and particularly to FIGURE l thereof, there is illustrated a tape 10 on which is provided mixed base information in the form of indicia located along the length of the tape at positions having significance in mixed base notation. More particularly, the tape 1) may be divided into successive longitudinally spaced imaginary lines shown in FIGURE 1 as lines 11, 12, 13, 14, 15 and 16, each line representing a code position. Proceeding from left to right transversely of the tape, four positions are provided, the first of which is utilized for inserting a reset pulse R, located at the line 17 longitudinally of the tape, and the remaining three transverse positions 18, 19 and 20 being reserved for the different bases, respectively, of mixed base coded words. Assuming use of a 3, 4, code, i.e., a code utilizing a base 3 in the first position, the base 4 in the second position and the base 5 in the third position, live coding positions are required longitudinally of the tape. Indicia are placed on the longitudinal line 13 in coincidence with the transverse lines 11, 11 aiid 12, or 11, and 12 and 13, for numerical values 1, 2, 3, respectively, i.e., at line 11 only to represent the value l, at line 11 and 12 to represent the number 2, to the base 3, or at lines 11, 12 and 13 if the number 3 is to be represented to the base 3. On the longitudinal line 19 are inserted similarly a number of indicia representative of a mixed base number to the base 4, and on the longitudinal line 20 is inserted a sequence of indicia representative of a number to the base 5. In each case the number of indicia represents the number. Accordingly, the coded tape 10, as illustrated in FIGURE 1 of the accompanying drawings, represents the numerals 1, 2, 4 to the bases 3, 4, 5, or moduli in mixed base nomenclature.

It will be appreciated that other types of codes may be employed in the present system if desired, and that a wide variety of indicia may be employed, as for example, magnetic indicia, punched holes, conductively coded spots and the like. It will be further appreciated that any desired number of bases maybe employed in the system and that the bases 3, 4, 5 are described as employed in the exemplary embodiment of the present invention for the sake of simplicity only.

It is assumed that data to be transmitted has been converted to mixed base code and has been inserted on a tape, such as 10. The problem posed for solution by the present invention is that of transmitting the information from the tape to a remote location by means of various types of modulation and the demodulation of the transmitted information, at such remote locations. To this end four read-outs A, B, C, D are provided, for readout of reset pulses and for reading out the indicia at lines 18, 19, respectively.

Referring now more particularly to FIGURE 2 of the accompanying drawings, there is illustrated a transmitter for generating pulse amplitude modulated pulses representative of mixed base information. It is assumed that the read-out terminals of the tape read out device of FIGURE l areconnected, respectively, to the correspondingly lettered terminals of the system of FIGURE 2, i.e., that the reset indicium 17 when sensed will be applied by means of the terminal A of FIGURE l to the terminal A of FIGURE 2 and will be applied to reset all the three rings of 3, 4, 5 identified by` the reference numerals 30, 31 and 32. It is further assumed that the base 3 readout B, the base 4 read-out C and the base 5 read-out D are, respectively, connected to the ring of 3 read-in terminal B of FIGURE 2, to the ring of 4 read-in terminal B, of FIGURE 2 and to the ring of 5 read-in terminal D of FIGURE 2. It is assumed that the rings initially are set to zero, and are stepped around in response to pulses provided at the read-in terminals B, C and D as the indicia on tape 10 ride under the sensing elements.

In FIGURE 2 the ring of three, 30 is 'connected at its three output terminals in series with resistances R1, R2, R3, respectively, which may all be equal and are relatively large. Resistance R1 leads through junction 37, and three resistances 34, 35 and 36 to ground. The resistances 34, 35 and 36 may all be equal and may be much smaller than the resistances R1, R2, R3. The resistance R2 proceeds to the junction 38 of resistances 34, 35 and the resistance R3 to the junction 39 of resistances 35 and 36. As seen from the terminal 37, 3S or 39, the ring of 3 and the very large resistances R1, R2, R3 at the outputs thereof appear as a constant current generator. It follows that a voltage is developed between the terminal 3'7 and ground which depends upon which one of the junctions 37, 38, 39 has current applied thereto from the ring of three, 30. Moreover, the voltage which will appear at the junction 37 may have one of three quantized values, the smallest of which exists when currentis applied to the terminal 39, the next higher one of which exists when current is applied to the terminal 38, the highest one of which exists when current is applied to the terminal 37.

A resistance network generally indicated by the refernece numeral 4d, is employed in conjunction with the ring of four, 31, and generates one of four quantized values at the junction point 41 in dependence upon the setting of the ring of four, 31. Additionally, a further resistance network 42 is applied to the output of the ring of ve, 32 for the purpose of generating tive quantized voltages at output terminal 43. Since the general philosophy of the networks employed for generating the quantized voltage is the same for each of the ring counters, further explanation of the operation thereof is dispensed with.

It is now clear that quantized values of voltages will appear at the terminals 37, 41 and 43. These values persist until the tape reaches its iifth longitudinal position, at which time the maximum possible mixed base read-out has been inserted in the ring counters 30, 31 and 32. Upon attaining the sixth position of the tape 10, a reset pulse is applied to the terminal A. This reset pulse proceeds via a lead 45 to a trigger source 46, which triggers a first pulse generator 47. The latter applies a gating pulse to the normally closed gate 48, and permits voltage from the terminal 37 to proceed to the output terminal 50 of the modulator. Upon termination of the pulse of the rst pulse generator 47 and in response to the trailing edge thereof, a trigger pulse is applied via lead 51 to a second pulse generator 52. The latter applies a gating pulse to open the normally closed gate 53, transferring voltage from the junction 41 to the output terminal 50. On termination of the gating pulse generated by the second pulse generator 52 and in response to the trailing edge thereof, a further trigger pulse is applied via lead 54 to a third pulse generator 55, which supplies a gating pulse to open the normally closed gate 56, permitting the voltage at the terminal 43 to be applied to the output terminal 5i). Shortly thereafter the reset pulse which had, during the gating operation, been delayed in the delay device 5'7, is applied via leads 58, 59 and 59A to reset the rings 30, 31 and 32, in preparation for insertion of a succeeding set of mixed base numbers from the tape 10.

At the output terminal, 50, appears then three sequential pulses having pulse heights which are coded in accor-dance with a mixed base code, in accordance with the information inserted into the input terminals B, C, D of ring counters 30, 31 and 32.` The typical appearance of a wave form provided at the output terminal 50 is that shown in FIGURE 3 of the accompanying drawings, wherein the dotted lines indicate possible quantized amplitude values andthe full lines represent an actual code representation of the number 2, 3, 4 in mixed base notation to the base 3, 4, 5.

Tie kpulses are transmitted in succession, the lirst pulse 60 being to the base 3, the second pulse 61 being to the base 4, and the third pulse 62 being to the base 5. The total transmission times of the pulses may be extremely short, i.e., burst` transmissions may be utilized, and the three pulses taken together represent sixty bits of information in terms of the twelve possible quantized amplitude values o the three pulses taken collectively.

The sequence of amplitude modulated pulses appearing at the terminal S may be transmitted to a remote point via a radio link, a Wire link, or in another conventional fashion, and may be there detected in conventional fashion, and applied toL an input terminal S0 of a demodulator system, illustrated in FIGURE 4 of the accompanying drawings. In the system of FIGURE 4, and connected in parallel to the input terminal 80 are a first pulse extractor 81, a .normally closed second pulse gate 32 and a normally closed second pulse gate 83. The tirst pulse extractor S1 is of conventional character per se, and is a normally open gate circuit which responds to ya iirst of a group of pulses and' thereafter cuts itself off for a predetermined period.` A typical such device is a mono-stable ilip-ilop.

In accordance with the present invention, the off-gated `period of tirst pulse extractorfcl is made sutliciently long that a group of two following amplitude modulated pulses may be provided to the terminal 940 while the circuit is gated oil. A second pulse gate d2 is normally closed, but is turned on for a short interval encompassing the second of the received pulses, in response to passage of' the iirst pulse by the rstfpulse extractor 31. Similarly, a third pulse gate 83 is' turned on in response to passage of the second of three'pulses by the second pulse gate d2. The output of the first pulse extractor 81, the second pulse gate 82, and thethird pulse gate 03, are applied respectively to amplitude discriminators :34, 85 and 8d. The amplitude discriminator 84 is a modulo 3 discriminator, i.e., it includes three chan- `nels for selecting three discrete` levels of input signal corresponding with the three levels that may be encountered in the iirst of the pulses transmitted by .the system of FIGURE 2. On a similar basis the amplitudediscriminator S5' is modulo 4 and the amplitude discriminator Se is modulo 5. There are, accordingly, three output terminals 37, for the amplitude discriminatori Srl, four such terminals 38 for the amplitude discriminator 85, and iive such terminals 89 for the amplitude discriminators S6. The output of the system is accordingly a mixed base coded group of signals, employing the bases or moduli 3, 4, 5, i.e., the same bases as were utilized for the input signal.

Referring now more particularly to FIGURE 5 of the accompanying drawings, there is illustrated a system for converting mixed base coded pulses into pulse width modulated pulses. identical elements of the systems of FIGURES 2 and 5 are identified by the same numerals of reference and description of these elements in connection with the description of the system of FIGURE 5 is accordingly dispensed with. It is assumed that at terminals 41 and 43, respectively, appear voltages having amplitudes representative or the three values of a mixed base number having the bases 3, 4 and 5. In cascade with the terminal 37 is `connected a full Width normally closed gate 90, which in response to a trigger supplied by a trigger source 91 opens for a predetermined v the output of the full width gate 90 having a predetermined width and an amplitude proportional to the voltage at the terminal 37'.

In cascade with the full width gate is provided an integrating circuit 92, shown in simple conventionalized form, as consisting of a series resistance 93 and a shunt capacitor '94.. Obviously, more sophisticated types of integrator circuits may be employed, it desired. At the output terminal 95 of the integrator 92 appears a sawtooth Voltage which rises at a rate determined'by the pulse amplitude of the signal being integrated. The Voltage at the terminal 95 is applied to a pulse width generator 96, which generates a pulse only while the voltage at terminal 95' is below some predetermined value. Accordingly, at the output terminal 97 of the pulse Width generator 36 appears a pulse having a width which is an inverse function of the height of the pulse provided by the full width gate 90.

The pulse width generator 9o may typically comprise a flip-flop circuit, which is started in response to a trigger pulse supplied by trigger source 91 via lead 98 and which is terminated when the amplitude of the integrator voltage at terminal 95 reaches a predetermined value. However, other types of devices for converting pulse amplitude to pulse width may be employed in the practice of the present invention, and I do not deire to be limited to any specic type of pulse height to pulse width conversion device.

The trailing edge of the full width gate 90 may, with suitable delay, be applied to a lead 99, which thenacts to trigger a full width gate 100, which is in cascade with the terminal 41 pertaining to the modulus 4. In cascade with the full width gate 100 is an integrator circuit 101 and a pulse width generator 102, the latter beingconnected via lead 103 to the output lead 97. There is, accordingly, in cascade with the terminal 41 a voltage to pulse width conversion circuit which operates precisely as does the circuit pertaining to the modulus 3 but which derives its voltage amplitude at the terminal 41. The trailing edge or" the pulse provided by the full width gate 100 maybe applied to a lead 104, and thence is applied to the full Width gate 106, and the pulse width generator 107, which are in cascade with the terminal 43 pertaining to the modulus 5. The output of the pulse width generator 107 is applied via lead 103 to the output lead 97.

In operation then the voltages at the terminals 37, 41 and 43 are sampled in time sequence, and caused to generate in the full Width gates 90, 100 and 106, respectively, pulses having predetermined width which are all equal, but having amplitudes which represent the amplitudes ofthe voltages at the terminals 37, 41 and 43. The amplitude modulated pulses of uniform width so generated are integrated in conventional integrators, one pertaining to each of the modular channels. Concurrently with initiation of operationy of each full width gate, as 90, 100 and 106 a pulse of constant amplitude is initiated in each of the `channels at the pulse width generators 95, 102. and 107, so that these pulses are generated in sequence. Each of these pulses is, however, cut ott upon attainment in the integrators 92, 101, 103, respectively, of predetermined amplitudes of integrated signals, times of attainment` of which are direct functions of the amplitudes of the pulses applied to the integrators. Accordingly, the widths of the ultimately generated pulses, atV output lead 97 are inversely proportional to the amplitudes of the drawings, there is illustrated a pulse Width modulation 7 Vdemodulator'for converting the pulse width modulated signals provided by the system of FIGURE into mixed Jbase words. For the purpose of this discussion it is assumed that the pulse width coded group consisting of pulses l111B, 111, and 112 is applied to an input terminal 80, in the form of D.C. pulses. This implies that if transmission was by radio, that a suitable carrier receiver and detector exists antecedent to the terminal Sil.

The pulse train applied to the terminal dit is fed to three parallel channels comprising a lirst pulse extractor 81, a second pulse gate 82 and a third pulse gate 83, which correspond with the correspondingly numbered elements of the system of FIGURE 4. Thereby, the iirst pulse 11i) is channeled to an integrator 115, the second pulse 111 is channeled to an integrator 116 and the third pulse 112 is channeled to an integrator 117. Integrators 115, 116 land'117 are provided with output terminals V113, 119 Vand 120 and serve respectively to convert pulses supplied thereto to steady voltages having amplitudes proportional to the pulse widths. The voltages available at the terminals 118, 119 and 121i are applied, respectively, to amplitude discriminators 84, 55 and S6 which convert these amplitudes to mixed base coded words by selecting appropriate ones of the terminals 87, SS and 89. For the exemplary transmitted code word 2, 2, 2 for example, 'the second terminal of terminals S7, the second terminal of terminal S8 and the second terminal of terminal 59 Vwould be energized.

The third pulse gate 83 supplies a control pulse via a lead 122 to a discharge and reset pulse generator 123, at the termination of the last pulse 112, and the reset pulse is applied via lead 124 to the output terminals 118, 119 and 120 of the three integrators 115, 116 and 117, to discharge the condensers thereof in preparation for a succeeding pulse group.

Reference is now made to FIGURE 8 of the accompanying drawings, wherein is illustrated a system for converting a mixed base coded group of input signals, such as are provided by the system of FIGURE l, to a pulse position modulated group of pulses having mixed base signilicance. It is assumed, to simplify the explanation, that the rings of three, four and live, respectively, have been set by incoming pulses deriving from tape 1@ (FIG- URE l) to positions corresponding with the values of the incoming pulse groups, in a manner which has been hereinabove explained in detail.

` In consequence, and considering particularly the ring of three, 30, one of the three output leads 150, 151 and 152 is energized and the remainder are unenergized. A sync pulse generator 153 is provided, which periodically supplies a sync pulse, for initiating read-out of the ring counters 30, 31 and 32. The sync pulse generator 153 supplies a sync pulse, illustrated at 154i of FIGURE 9, to the ring of three, 30, via a lead 156, and simultaneously supplies that sync pulse to an output lead 155. The read-out pulse supplied to the ring of three, 3i), via the lead 156, effects read-out of the ring of three, 30, by applying a responsive pulse selectively to one ofthe leads 150, 151 and 152, which correspond with the count set into the counter. If the lead 150 is energized, an output pulse proceeds Via a delay device 161) to the output lead 155. The delay device 160 possesses a delay time T appropriate to one time channel of the system. If the lead 151 is energized, the pulse proceeds via the delay device 161 and 160 in cascade to the output lead 155. If the output lead 152 is energized, on the other hand, a pulse proceeds via delay devices 162, 161 and 161) in cascade, to the output lead 155. It follows that an information pulse will be applied to the lead 155 with a delay which corresponds with that one of the leads 150, 151 and 152 which have been energized, and correspondingly with the setting of the ring of three, 3d. The ring of four, 31, includes four output leads 167, 168, 169 and 170 which are connected to a cascaded set of four delay devices 171, each of which has a delay time T.

The delay devices 171 are connected in cascade with the ,delay device 162. Accordingly, the ring of four, 31, in response to a synchronizing pulse supplied over the lead simultaneously with a syinchronizing pulse supplied over the lead 156 to the ring of three, 30, eliects a readout of the ring of four, 31. This pulse reaches the input of the delay device 162 after a delay corresponding with the numerical value of the setting of the ring of four counter 31. By a similar technique, involving a cascaded set of delay devices 172, the ring of live, 32, if read-out. There are, in toto, twelve delay devices, each having the same delay time T, and which establish twelve time positions following the synchronizing pulse 154. One of the first three of these time positions (FIGURE 9) is occupied by a pulse according to the setting to the ring of three, Sil. One of the next four positions is occupied as a function of the setting of the ring of four, 31 and one of the remaining live positions is occupied according to the setting of the ring of live, 32. In FIGURE 9 is illustrated in dotted outline the possible pulse positions following the synchronizing pulse 154, and in full lines the occupied positions for a mixed base word 2, 3, 4.

. The pulses provided at the output lead 155 are transmitted to a remote point by means of a radio link or in some other convenient mode, where they 'are applied as D.C. pulses to an input terminal 2G11, of a PPM demodujlator (FIGURE l0). This implies that the necessary demodulation system or receiver device is provided -antecodant to the terminal Zlltl. The train of pulses applied to fthe terminal 2011 proceed to a sync pulse extractor 2611, which provides an youtput pulse in response to the sync pulse 154-, selecting the latter on the basis of its amplitude. The output pulse proceeds to a cascaded set of twelve delay lines, 202. The sync pulse extractor 2111 channels Ithe remaining pulses of the pulse train, excluding the sync pulse, to a common lead 2113, whence these pulses are applied in parallel via Ileads 2li-fl, 205 and 205 to a set of three coincidence gates 207, 208 'and 209; 'Iihe coincidence gates 207 comprise three gates, while lthe coincidence gates 208 and 209 comprise four and live gates, respectively, these gates being connected jointly to the leads 204, 205 and 206 for each set, and being connected individually via leads `such as 210 to the outputs of the several delay lines 202. It follows that one gate of each of sets 207, 208', 2119 will be selected, and will energize the corresponding ones of the output terminals 211 and the selec-tion will occur in accordance with the time positions of the received pulse train, since the delay devices 202 have delay times T which are precisely the same as the delay times T utilized for the cascaded del-ay devices of FIGURE 8.

In the system of FIGURE l1 lof the Iaccompanying drawings, three frequency modulated sub-carriers yare employed to represent the values of three numerals of a mixed base word. Mixed base signals are initially translated or converted into amplitudes of volt-ages, as in the system of FIGURE 2, of the accompanying drawings, these vol-tages appearing at terminals 37, 41 `and 43. The voltages there appearing are applied to a set of frequency modulators 25), 251 and 252, respectively, which in turn set the frequencies of sub-carrier oscillators 253, 254 and 255. Accordingly, the sub-carrier oscillator 253 may provide any one of three values, the sub-carrier oscillator 254 any one of tour values, and the sub-carrier oscillator- 255 any one of live values, since the moduili of the `system are 3, 4, 5.

Reference is made to FIGURE 12 of the accompanying drawings, which provides a plot of frequencies of subcarriers with respect to a main carrier frequency on [the assumption that the outputs of the sub-carrier oscilla-tors 253, 254, 255 are .applied to a common output lead 256 in which turn amplitude modulates an R.F. carrier. In FIGURE 11 the carrier is assumed to be 257 'and the subcarrier frequencies for code value of 2, 3, 4 are vshown -at 258, 259 and 260, respectively, the dotted ordinates in 9 FIGURE 11 representing possible positions for sub-carhier frequencies.

Two diferent systems are provided for ldemodulating the signals of the .type transmitted by the system of FIG- URE 11. In one of these systems the radio frequency carrier is detected in conventional fashion, so that the subcarriers may be removed and applied to an input terminal 270 of ,FIGURE 13. Terminal 276l is connected in parallel to three sets of filters, one of which consists of three filters, each tuned to a different one of the subcarrier frequencies assigned to the sub-carriery oscillator 253, of FIGURE 10, the other set consisting of four parallel kfilters 274, 275, 276 and 277, `which are tuned, respectively, to accept selectively the sub-carrier oscillator fre* quencies available to the sub-carrier oscillator 254, the remaining group of `filters 27S to 282, inclusive, respectively, being each tuned to 4a different one of the frequencies avail-able to the sub-carrier oscillator 255. The signal outputs yof the filters 271, 273, inclusive, `are used to set a ring of three counter 283 to a value corresponding with `the filter which is energized, Similarly, the set of filters 274-277, inclusive are used to `establish a setting for a ring of four counter, 284, in correspondence with the filter which is selectively energized, while the set fof filters 273.282, inclusive, establishes a setting for a ring -of live counter 285. Accordingly, the `out-put terminals 286, 287 and 253 of the several rings `are energized in mixed base notation in accordance with the transmitted signal.

ln accordance with a modification of the system of i FlGURE 13, illustrated .at FIGURE 14 of the accompanying drawings, instead of utilizing discrete filters for detecting the several sub-carrier frequencies, frequency discrimina-tors are employed. The `outputs `of these are then .selected by means of amplitude discrirninators 'Ilo this end, the input terminal 27d supplies signal to three frequency discriminatous Still, 3011, and 302, in parallel. 'Ilhe ydiscriminator 300 provides one of three amplitudes of output signal according to which yof the three modulo three sub-carriers are transmitted. Likewise, the fre,- quency d-iscriminator 301 provides four discrete levels of DC. output, and the frequency discriminator 302 provides live `discrete levels of output. Accordingly, lat the output terminals 303, 304 and 305 of the frequency discrimin-ators Sud, 391 and 362 appear three D.C. levels representative of the three sub-carrier frequencies. These DC. levels are separated by means of amplitude disc-riminators 306,

307 and 33S, as in FIGURE 4, and accordingly, one output lead is selected from each of :the sets of leads 286, 287, 288.

While a mixed base system employing moduli 3, 4, 5 has been described for exemplification, in the `description of the present system, which provides a resolution of one part 4in sixty, resolutions `of this order can be more easily obtained through simple analogue transmission methods. The significant advantages of mixed base techniques become more evident as the number of moduli, or the modulo values themselves, are increased. For example, a 5, 6, 7 combination will yield data transmission aceuraoies in the yorder of `0.5% whereas no circuit is required to read a parameter :to an accuracy of better than 14%; and no more than 18 parallel circuits are involved. 'Ille advantages of iiash communications are noteworthy and .this type of communication is particularly advantageous in connection with mixed lbase techniques. For example, ya sequential trisrnodulo mixed base group of pulses, and Where parallel transmission occurs, such as in the subcarrier frequency embodiments of FIGURES 11-14, inclusive, a total of 425 micro-second may be required to transmit one word.

insofar as the system of FIGURE 15 corresponds with the system of FIGURE 3 of the accompanying drawings, identical elements have been identified by the same numerals of reference, and their description is dispensed with. There is, accordingly, in the system of FiGURE 15, available three voltages, at the terminals 37, 41 and 43,

pulse source 321. The pulse source 321 providesa single n pulse to a pulse amplitude modulator 322 and to a pulse width modulator 323. The pulse width modulator 323 generates a pulse having one of four widths, selected in accordance with the setting of the ring of four, 31, and applies this pulse to an amplifier 324. The latter is controllable in respect to the amplitude of its output in response to an amplitude control voltage, which in fact constitutes the output` pulse from the pulse amplitude modulator 322 and is applied to the amplilier 324 by means of a lead 325. Accordingly, an output lead 32e, deriving from the amplifier 324, carries a single pulse the' width of which represents the setting of the ring of four, 31, and the amplitude of which represents the setting of the ring of three, 3l). The voltage available at the terminal 43wl1ich represents the setting of the ring of live, 32, is applied to a frequency modulator 327, setting the frequency of the latter at one of five possible values. The output of the frequency modulator 327 is accordingly a CW signal having one of the five permissible frequencies, and is applied to an amplitude modulator 328 which is pulsed by the signal arriving over the lead 3126. The output signal derivable from the amplitude modulator 328 is accordingly a pulse' carrier having afrequency which is a function of the setting of the ring of live, 32, the pulse having a width representative of the setting of the ring of four, 31, and the height of the pulse being representative of the setting of the ring of three, 36. The pulse so generated is applied to an RF. modulator, 329, which modulates an extremely high frequency carrier, and transmits same to a remote location over an antenna 336. The total duration of the pulse generated may be considerably less than one-microsecond, i.e., burst transmission techniques may be employed.

Following transmission of the burst, the reset pulse applied to the terminal A arrives at the rings of 3, 4, and 5 identified by the reference numerals 3l), 3l and 32, via a delay device 57 and the leads 331, 332 and 333 respectively, and serves to reset these counters in preparation for a following readout from tape lll. The system of FIG- URE16 representsin block diagram a demodulator for the signals generated by the system of FIGURE 15. In the system of FIGURE 16 is provided au antenna 341 which is coupled with an RF. detector 342. At the output terminal 343 of the latter is provided a sub-carrier signal in the form of an amplitude modulated and width modulated pulse carrier, such as is provided by the amplitude modulator 328 of FIGURE 15. This pulse isapplied via a lead 244 to a frequency discriminator 345, at the output of which appear one of live DC. levels in correspondence withthat one of the live available sub-carrier frequencies generated by the frequency modulator 327. These are amplitude discriminated in an amplitude discriminator 346 and applied selctively to the leads 347,

that one of the leads 347 being energized which representsk the amplitude of the D C. output of the frequency discriminator 349. The signal appearing at the lead 359 is a pulse sub-carrier. It is detected in two separated channels. In one of these channels is provided a subcarrier demodulator or detector 35@ which provides at its output a D.C. pulse having the amplitude of the pulse provide by the pulse amplitude modulator 322. This pulse is applied to an amplitude discriminator 351, which selects one of the output leads 352, according to the amplitude of the input pulse. i

'In a second channel is yprovided a further sub-carrier detector 3.54, the output of which is applied to a pulse type limiter 355, at the output of which appears a pulse which is of uniform height, regardless of the amplitude of the to the amplitude of the input pulse.

At the output terminals 352, 358 and 347 corresponding with the mixed base moduli 3, 4 and 5 there is, accordingly, provided signals representative of the settings of the ring counters 39, 31 and 32 which in turn represent indicia in mixed base notation read-out of the storage tap l@ of FIGURE 1.

It will be clear that the system of FIGURES and 16 may be modified in respect to the moduli employed, in any one of the channels. For a 3, 4, 5 base system for example, frequency may represent the modulus 3, pulse width may represent the modulus 5 and pulse height may represent the modulus 4. It will be further clear that, in place of pulse width, pulse position may be employed as one of the modulating devices, i.e., that three mixed base digits may be transmitted to a remote location and there be demodulated, by means of a system in which one digit is transmitted in the form of pulse position, one digit in the form of pulse height, and one digit in the form of pulse carrier frequency.

While I have described and illustrated various specific embodiments of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as deiined in the appended claims.

What is claimed is:

l. In combination, a plurality of ring counters each having a different base, means for setting each of said ring counters to a number, the array of numbers corresponding with the settings of said ring counters representing a mixed base word, a separate network in cascade with each of said counters for converting the settings of said counters to signal amplitudes representative of the settings of said counters, and means for converting said signal amplitudes to pulse coded signals.

2. The combination according to claim l, wherein said means for converting includes means for converting said signal amplitudes to pulse amplitude modulated signals.

3. The combination according to claim l, wherein said means for converting includes means for converting said signal amplitudes to pulse width modulated signals.

4. The combination according to claim 1, wherein said means for converting includes means for converting said signal amplitudes to pulse frequency modulated signals.

5. In combination, a rst ring counter modulo n, a second ring counter modulo m, Where m and n are relaltively prime, means for inserting into said first and second ring counters the elements of a two element Word in a mixed base code based on moduli m and n, said iirst ring counter having m output terminals corresponding respectively with m counters, said second ring counter having n output terminals corresponding respectively with n counts, a separate relatively high resistance in cascade with each of said terminals of said iirst counter and of said second counter, m relatively small resistances joining said.=high resistances operatively associated with said first counter to each other and to a point of reference potential and so arranged that a`voltage is developed across all said relatively small resistances which represents the count of said first counter, n relatively sma-ll resistances joining said high resistances operatively associated with said second counter and so arranged that a voltage is developed across all said last named small resistances which represents the count of said second counter.

6. In combination, a irst ring counter having a base modulo m, a second ling counter having a base modulo n, where m and n are relatively prime, rst network "i2 Y means connected to said ilrst ring counter for deriving therefrom a vol-tage having m discrete possible values representative of and responsive to the count of said hust ring counter, second network means connected to said second ring counter for deriving therefrom a voltage having n discrete possible values representative of and responsive to the count of said second ring counter.

7. The combination according to clainr 6 wherein is Ifurther provided means for reading out said voltages in sequence.

8. The combination according to claim 6 wherein is ftuther provided means for translating each of said voltages into la pulse of width representative of one of said voltages.

9. The combination according to claim 6 wherein is further provided means for translating each of said voltages into a pulse having a position representative of amplitude of one of said voltages.

1t). The combination according to claim 6 wherein is further provided means `for translating each of said voltages into ya signal of frequency representative of amp1i tude of one of said voltages.

11. In a mixed base system of telemetering, a plurality of ring counters having maximum `counts which `are relatively prime, means for converting the instantaneous counts of said ring counters into voltages having amplitude values representative of said instantaneous counts of said ring counters, means for converting said voltages to pulses, `and means for transmitting said pulses to a remote point.

l2. In a mixed base system of telemetering, a plurality of ring counters having maximum counts which are relatively prime, means for converting the instantaneous counts of said ring counters into signals having amplitudes representative of said instantaneous counts, and means for converting said signals for each instantaneous count to a pulse having a iirst pulse characteristic representative of the instantaneous count of one of said ring counters, and having a funther characteristic representative of the instantaneous count of another of said counters.

13. The combination according to claim l2 wherein is further provided means for transmitting said pulse to a remote location, and means lfor receiving `said pulse at said remote location and there decoding said pulse to recover the counts of said ring counters.

14. The combination according to claim 8 wherein said means for converting includes means for sequentially converting said signal amplitudes to pulse coded signals.

l5. A system for transmitting and decoding information represented in mfmed base notation, said notation including N dilferent mioduli, where N is any integer greater than one, said moduli being relatively prime numbers, comprising a first set of N rings, each having a different maximum count, said maximum counts being respectively equal to said moduli, means responsive to said information for loading each ring of said first set `to a count representing said information, said information representing count being any number between zero and one less than the maximum count in the respective modulus, means deriving a separate output from each count position of each ring of said first set, means: responsive to the outputs of the count loaded into said iirst set of rings for transmitting a group of pulse coded signals to a remote location, said group of pulse coded signals including information regarding the count ot each modulus, means at the remote station for receiving and decoding said group of pulse coded signals, said last named means comprising a second set of N rings each |having a different maximum count respectively equal to said moduli, and means responsive to the received group of pulse coded signals for loading each ring of the second set to a count representing the information in the received group of pulse coded signals, said last named means including means `for feeding information regard- 13 ing the kth modulus to the ring of the second set for the kth modulus, where k is every one of the N moduli.

16. The lsystem of claim 15 wherein said'means for transmitting includes means for deriving amplitude modulated pulses.

'17. The system of claimt l5 wherein said means for transmitting includes means for deriving wid-th modulated pulses.

18. The system of claim 15 wherein said means for transmitting includes means for deriving position mod ulated pulses.

19. The system of claim 15 wherein said means for transmitting includes means for deriving frequency modulated pulses.

20. The system, of claim 15 wherein N=3, land said means for transmitting includes means for deriving a single pulse Ifor each mixed base word, said last named means including means for amplitude modulating said single pulse in response -to the count of one of the rings of said first set, means for pulse width modulating said Single pulse in response to the count of another ring of said first set, and means for frequency modulating the carrier of said pulse in response to the count of still another ring of said 'first set.

21. The system of claim 15 wherein said means for transmitting includes means responsive to the count of one ring of said first set for frequency modulating said group of pulse coded signals, and means responsive to ltlie count of another ring of said first set for further modulating said group of puise coded signals.

22. A system for transmitting information represented in mixed base notation, said notation including N different moduli, Where N is any integer greater lthan one, said moduli being relatively prime numbers, comprising N rings, each lhaving a different maximum count, said maximum coun-ts being respectively equal to said moduli, means responsive to said information for loading each ring to a count representing said information, said information representing count being any number between tzero and one less than the maximum count in the respective modulus, means deriving a separate output from each `count position of each ring and means responsive to the outputs of and the count loaded into said rings for transmitting a group of pulse coded signals to a remote location, said group of pulse coded signals including information regarding the count of each modulus.

References Cited in the file of this patent UNITED STATES PATENTS 2,275,017 McNaney Mar. 3, 1942 2,756,274 Stenning July 24, 1956 2,772,399 Jacobsen Nov. 27, V`1956 2,796,602 Hess et al June 18, 1957 2,810,518 Dillon Oct. 22, 1957 2,852,745 Kohn Sept. 16, 1958 2,964,241 Rosenberg et al. Dec. '13, 1960 2,997,541 Grottrup Aug. 22, 1961 3,023,277 Mathews Feb. 27, 1962 OTHER yREFERENCES Murphey: Basics of Digital Computers, vol. 1, copyright June 1958, p. 27. 

15. A SYSTEM FOR TRANSMITTING AND DECODING INFORMATION REPRESENTED IN MIXED BASE NOTATION, SAID NOTATION INCLUDING N DIFFERENT MODULI, WHERE N IS ANY INTEGER GREATER THAN ONE, SAID MODULI BEING RELATIVELY PRIME NUM BERS, COMPRISING A FIRST SET OF N RINGS, EACH HAVING A DIFFERENT MAXIMUM COUNT, SAID MAXIMUM COUNTS BEING RESPECTIVELY EQUAL TO SAID MODULI, MEANS RESPONSIVE TO SAID INFORMATION FOR LOADING EACH RING OF SAID FIRST SET TO A COUNT REPRESENTING SAID INFORMATION, SAID INFORMATION REPRESENTING COUNT BEING ANY NUMBER BETWEEN ZERO TION REPRESENTING COUNT BEING ANY NUMBER BETWEEN ZERO AND ONE LESS THAN THE MAXIMUM COUNT IN THE RESPECTIVE MODULUS, MEANS DERIVING A SEPERATE OUTPUT FROM EACH COUNT POSITION OF EACH RING OF SAID FIRST SET, MEANS RESPONSIVE TO THE OUTPUTS OF THE COUNT LOADED INTO SAID FIRST SET OF RINGS FOR TRANSMITTING A GROUP OF PULSE CODED SIGNALS TO A REMOTE LOCATION, SAID GROUP OF PULSE CODED SIGNALS INCLUDING INFORMATION REGARDING THE COUNT OF EACH MODULUS, MEANS AT THE REMOTE STATION FOR RECEIVING AND DECODING SAID GROUP OF PULSE CODED SIGNALS, SAID LAST NAMED MEANS COMPRISING A SECOND SET OF N RINGS EACH HAVING A DIFFERENT MAXIMUM COUNT RESPECTIVELY EQUAL TO SAID MODULI, AND MEANS RESPONSIVE TO THE RECEIVED GROUP 